PODOLSK, Russia — As a former Soviet factory director, Vladimir Melikhov survived the brutal business turf wars of the 1990s to make a fortune in construction. Now he devotes his energy and money to what, in the Russia of President Vladimir V. Putin, has become a truly risky enterprise: digging into Russian history.

Mr. Melikhov has founded a private museum that is devoted to the memory of the “anti-Bolshevik resistance” and that delves into a singularly taboo topic — why many Cossacks and other persecuted Soviet citizens welcomed, at least initially, Hitler’s invasion of the Soviet Union in June 1941.

The museum, housed in a three-story building he built himself on his private estate in Podolsk, south of Moscow, makes no attempt to glorify Nazi collaborators. But it has enraged the authorities by focusing on the relentless persecution that followed Russia’s 1917 Bolshevik revolution, creating fertile ground for anti-Soviet treachery during a war that cost 25 million Soviet lives.

“What they really don’t like is that I make people think about what happened in the past and what is happening today,” Mr. Melikhov said.

As a result, he has been denounced on state television as a traitor, Russian border guards have defaced his passport to prevent him from leaving the country, and he has faced a string of seemingly trumped-up criminal charges. Last week, a court in Podolsk found him guilty of illegal weapons possession and sentenced him to a year of “restricted freedom” — house arrest or some other limits on his movements.

The hostility of the Russian state toward Mr. Melikhov is a measure of how the history of World War II, which Russians know as the Great Patriotic War, is a delicate topic — particularly at a time when Mr. Putin and his allies constantly refer to the conflict to fortify their legitimacy.

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A Nazi poster claiming that the German Army was the defender of the Soviet people. The museum is housed in a building Mr. Melikhov built himself on his private estate.CreditJames Hill for The New York Times

They cast themselves as the true heirs of wartime patriots and vilify their foes — like the anticorruption campaigner Aleksei A. Navalny, who orchestrated nationwide protests against the Kremlin last week — as sellouts akin to Nazi collaborators.

With communism ditched and liberal capitalism largely discredited as an alternative, the Soviet Union’s victorious 1941-45 struggle against Nazism has become the untouchable cornerstone of a new state ideology built around a sanitized history of patriotic sacrifice, discipline and national unity.

“The myth of the Great Patriotic War is the founding myth of contemporary, post-1991 Russia,” said Serhii Plokhii, a Russian-born history professor at Harvard. “Anything that challenges that myth, understood as the victory of the unified Russian people over the hostile West, or introduces shades of gray into the black-and-white picture of the battle between good and evil, is rejected and attacked.”

Mr. Melikhov is not the only one to be singled out. A state committee in Moscow recently vetoed a decision by scholars in St. Petersburg to award a doctoral degree to Kirill Alexandrov, a historian. His dissertation, on the Committee for the Liberation of the Peoples of Russia, an outfit set up in 1944 with German support to rally opposition to Stalin’s regime, was deemed insufficiently patriotic.

Mr. Melikhov believes that his principal crime, as far as officials are concerned, is not just the matter-of-fact treatment of reviled traitors at his museum in Podolsk, and another museum of his near Rostov-on-Don in southern Russia.

A bigger problem, he said, is that any open discussion of the choices Russians made during the war undermines Mr. Putin’s efforts to rally Russia around the heroism of the past and his hostility to the internal and external enemies that the Kremlin presents as besieging the country.

“The Soviet Union collapsed, but the Soviet system of rule and thinking has stayed the same,” Mr. Melikhov said. “There was monopolization of political power, monopolization of economic power, monopolization of mass media, monopolization of civil society. Today, the basic elements of this Soviet system are all being put back in place.”

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A display about the famine of 1922. The photographs have been cited in court cases against Mr. Melikhov.CreditJames Hill for The New York Times

The evidence presented against Mr. Melikhov at his trial consisted of a rusty 19th-century gun from his museum collection and a stash of bullets that did not fit any weapon in his possession. Mr. Melikhov said investigators had planted them.

“I struggled against many bandits in the 1990s, but now it is even worse: You can’t fight back against our officials,” he said in an interview at his estate, a fenced-in compound of brick buildings, lush gardens and a pond built atop a Soviet-era waste dump.

If not for his interest in history, Mr. Melikhov, 60, would seem a good fit with Mr. Putin’s vision of a resurgent Russia built around traditional values and muscular patriotism.

Mr. Melikhov is a descendant of Cossacks, the rugged horsemen who secured the frontiers of the Russian empire and whose members have been in the forefront of various nationalist causes since the 1991 collapse of the Soviet Union. He is also an Orthodox Christian and has built a handsome wooden church next to his house in Podolsk.

But years of work collecting and reading old books and documents have convinced Mr. Melikhov that what Mr. Putin and his allies in the Orthodox Church and elsewhere celebrate as Russian tradition grossly distorts the past.

He said that while Mr. Putin had helped lift Soviet-era suspicion of Cossacks, who mostly sided with anti-Bolshevik forces during Russia’s 1917-22 civil war, he had forgotten the core of the Cossack creed.

“The most important value for a Cossack has always been his own freedom,” Mr. Melikhov said.

That reading of Cossack tradition, which many still associate with pogroms and brutal service to an expanding Russian empire under the czar, has helped Mr. Melikhov win unlikely support from Russian liberals.

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Mr. Melikhov, a descendant of Cossacks, with a painting depicting the forced repatriation of Cossacks by the British in 1945. “The most important value for a Cossack has always been his own freedom,” he said.CreditJames Hill for The New York Times

One prominent fan is Andrey Zubov, a liberal historian who was removed from his post at a prestigious Moscow institute after he compared Mr. Putin’s 2014 seizure of Crimea from Ukraine to Hitler’s annexation of territory in 1939. Mr. Zubov promptly earned himself a place on a list of “traitors” assembled by Mr. Putin’s supporters.

“Communism is obviously dead as an ideology,” he said. “There is no communism. But there is a Soviet way of thinking, a Soviet form of imperialism that survives and that authorities want to protect from historical facts.”

Calling someone a traitor, Mr. Zubov added, shuts down all discussion: “A traitor is an enemy, something awful, but it has become just another way for our authorities to describe somebody who merely has a different point of view.”

A website called predatel.net, which translates as traitor.net, features a list of Moscow intellectuals and others who are deemed to have betrayed their country, and invites readers to fill in a form and “suggest a traitor” to add to the list.

Who stands behind the website is a mystery, but its mission meshes with a message promoted tirelessly by the Kremlin and state-controlled media since the crisis in Ukraine in 2014: Russia is under threat from within and without by enemies that must be exposed and defeated.

Mr. Melikhov said the latest case against him had been orchestrated not by local prosecutors in Podolsk but by the Federal Security Service in Moscow, the domestic intelligence arm of the old Soviet K.G.B., after he publicly supported an anti-Kremlin political party before parliamentary elections last year.

He also opposed the annexation of Crimea, the prime litmus test of supposed treachery, a charge that Mr. Melikhov said was being applied to those who merely disagreed publicly with the Kremlin.

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“What they really don’t like is that I make people think about what happened in the past and what is happening today,” Mr. Melikhov said of the authorities.CreditJames Hill for The New York Times

That, he said, is what makes his two museums so threatening: They prod the thousands of ordinary Russians who have visited to think about their own history and question simple labels like patriot and traitor. They also amplify questions that professional historians have quietly raised about official accounts of the war.

Those official versions tend to play down Stalin’s 1939 pact with Hitler, his murderous purge of military officers in the 1930s and the relentless persecution of perceived internal enemies before the Nazi invasion.

In the museum guest book, a visitor wrote, “Thank you to the creators and curators of this museum for the opportunity to look at those pages of our history that the official authorities try to hide from us.”

Determined to fortify the official line of heroic unity and almost superhuman endurance, the authorities have steadily restricted access to historical archives that opened up after the collapse of the Soviet Union.

They have also come down hard on scholars who question popular legends like the story of 28 guardsmen led by Maj. Gen. Ivan Panfilov who sacrificed themselves to help beat back German troops advancing on Moscow in the winter of 1941.

The longtime director of the Russian State Archive, Sergei Mironenko, was removed from his job last year after he exposed the story as “fiction” invented by Soviet propagandists.

In response, Russia’s deeply conservative culture minister, Vladimir Medinsky, declared that inconvenient historical facts should not be allowed to stand in the way of cherished national myths.

Wartime heroes like Panfilov and his men, the minister ordered, must be treated like “saints,” and those who cast doubt on their exploits are “scum” who “should burn in hell.”

Correction:

An earlier version of this article misstated when a court in Podolsk found Mr. Melikhov guilty of illegal weapons possession. It was last week, June 13, not “on Tuesday.”

Sophia Kishkovsky contributed reporting from Moscow.

A version of this article appears in print on , on Page A4 of the New York edition with the headline: Putin-Era Taboo: Dissecting Roots of Nazi Sympathy. Order Reprints | Today’s Paper | Subscribe